The present invention relates generally to the prediction of fatigue lives of aluminum alloys and, more particularly, to systems, methods, and articles of manufacture to predict fatigue lives of aluminum alloys under at least one of multiaxial proportional and non-proportional loading.
Fatigue life prediction of aluminum alloys, in particular, cast aluminum components, traditionally has been challenging not only because of microstructure complexity, but also because of uncertainty of defect population. Under multiaxial and, in particular, non-proportional loading, defects and microstructural discontinuities often play an important role in crack formation and fatigue properties. It is believed that the presence of defects and dislocation piling up and stacking near discontinuities may be attributed to local stress concentration and resultant fatigue crack initiation and propagation. The extent of the dislocation piling up and stacking near discontinuities may depend on not only a stress state present in the aluminum alloy, but also the loading path. Research has indicated that fatigue lives of aluminum alloys, such as 6063 and A356, under circular, non-proportional loading generally are much shorter than those under proportional loading with the same equivalent strain amplitude. The shorter fatigue lives may be due to maximum shear planes rotating and changing continuously during non-proportional loading. As a result, increasing numbers of dislocations are piled up and stacked near discontinuities during non-proportional loading, thereby, accelerating fatigue crack initiation and propagation and, thus, shortening the fatigue lives of aluminum alloys. As such, based on the foregoing, there exists a need for systems, methods, and articles of manufacture to accurately predict fatigue lives of aluminum alloys under multiaxial loading.